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Prosecutors: Search of his phone found texts from Michelle Carter urging him to commit suicide

Defense attorney says Carter is innocent and tried to get Roy to undergo counseling

(CNN)A Massachusetts teenager accused of involuntary manslaughter allegedly urged her online boyfriend to commit suicide, telling him in a text message, "The more you push it off, the more it will eat at you," according to a document released by the Bristol County district attorney's office.

"You need to do it, Conrad," Michelle Carter wrote her friend in the early hours of July 12, 2014, according to the document. "You're ready and prepared. All you have to do is turn the generator on and you will be free and happy. No more pushing it off. No more waiting."

Later that morning, Conrad Roy, 18, left his mother's home and drove to the parking lot of a Kmart, the document showed. He called Carter, spoke with her for more than 40 minutes and, at some point, got out of his truck "because (the carbon monoxide poisoning) was working and he got scared," according to the document.

Carter told him to get back in the truck, according to her indictment. The next day, on July 13, police found his body in the truck; he used a combustion engine to fill the cabin with carbon monoxide.

Carter, 18, was indicted in February, but the text messages exchanged between the two were released late last month in a prosecution response to a defense motion seeking to dismiss the indictment.

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Carter's attorney, Joseph Cataldo, has maintained his client's innocence, saying the evidence will show it's not a manslaughter case and that Carter attempted to console Roy on many occasions. Cataldo said Roy had planned the suicide for months.

Cataldo said his client had repeatedly encouraged Roy to seek professional help and finally resigned herself that he would carry out his plan. The lawyer said the case was a "dangerous prosecution" in that it suggests "speech alone caused" the young man to kill himself.

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After searching Roy's cell phone, police discovered hundreds of texts between the two teenagers, many with language from Carter encouraging Roy to take his life, according to police.

In text messages between July 6 and July 12, 2014, "Carter assisted Conrad's suicide by counseling him to overcome his doubts, devising a plan to run a combustion engine within his truck ... and by directing him to go back in his truck after he exited it, when he became frightened and said the plan was working," according to a court document.

"I think your parents knowyou're in a really bad place...They know that you're doing this to be happy and I think they will understand and accept it. They will always carry you in their hearts," Carter wrote in one text.

"Aww. Thank you, Michelle," he wrote back.

According to the document, Carter even offered technical advice on carrying out the suicide.

"If you emit 3200 ppm of (carbon monoxide) for five or ten minutes you will die within a half hour," she wrote. "You lose consciousness with no pain. You fall asleep and die."

Since his death, photos and messages about Roy have been posted to a Twitter page that the district attorney's office confirmed to be Carter's. One reads, "I can't believe today already marks 4 months without you. I love you and miss you always Conrad..."

In September 2014, Carter organized a softball tournament in Roy's memory and raised $2,300 for mental health awareness, according to police.

Carter was arraigned on February 6 in New Bedford Juvenile Court and released on $2,500 bail and told not to use social media, according to Gregg Miliote, a spokesman for the Bristol County district attorney's office.

Carter was indicted as a youthful offender because she was not 18 at the time of Roy's death. Youthful offenders are tried in juvenile court, but the proceedings are public.